1. Field of the Invention
The invention is directed to tie downs for securing cargo in aircraft.
2. Background
Stabilizing cargo during shipment is an important objective of aircraft cargo transport systems. In addition, aircraft cargo transport systems should be flexible enough to adapt to conditions during loading, stowage and unloading of the cargo. Typically, cargo shipped by air is first loaded onto specially configured pallets, or into specially configured containers commonly referred to as Unit Load Devices (“ULDs”). Cargo is loaded, stowed and secured within the aircraft for shipment. The cargo deck, roller trays, and sidewalls of a cargo compartment typically include a plurality of restraint devices attached at various installation points located on the cargo deck and sidewalls that can be used to engage and secure cargo.
Two types of devices typically used to secure cargo during shipment are primary and supplemental restraint devices. Primary restraint devices are stationary and positioned at predetermined installation points on a cargo deck or roller tray. Predetermined installation points, however, may not provide optimal attachment locations for securing a ULD. Often, cargo may not fit within the ULD and thus may not fit within the predetermined installation points. Supplemental devices are moveable and can be fixed to any location capable of receiving a supplemental restraint. Attachment locations for supplemental devices may be best determined by which location best minimizes lateral or longitudinal movement of cargo. The loader is tasked with optimizing the use of primary and supplemental restraint devices available at the time of loading and stowage.
The attachment location that minimizes cargo movement, however, may result in damage to the supplemental restraint device and the aircraft. Restraint straps can attach from numerous directions and angles and can place non optimal forces on supplemental restraint devices. For example, the position of the supplemental restraint device on a cargo deck may not align with the direction the restraint strap extends from the cargo. The optimal attachment location, therefore, may not adequately or optimally distribute load from the restraint to the cargo deck. Excessive forces and resultant damage to a restraint device undermine cargo stability. Thus, the ability to adequately distribute the load from the restraint strap to the attachment locations facilitates cargo stabilization. Moveable supplemental restraint devices that are also adaptable to distribute loads from the restraint to the cargo deck provide the loader with the flexibility needed to optimize cargo stabilization.
While movable supplemental devices provide increased flexibility for a loader, the “moveable” nature of these devices could lead to greater theft, loss or misplacement.
Thus, there is a need for supplemental restraints that are capable of attachment to a variety of locations along a roller tray, adaptable to the circumstances of loading and stowage of the cargo and that have design features that discourage theft or loss.